Conventionally, a transceiving device, such as a radar device, for transmitting and receiving high-power high-frequency signals using an antenna for both transmission and reception is provided with a high-frequency limiter in a route of the received signals (refer to Nonpatent Document 1).
FIG. 1 is a block diagram showing an example of arrangement of a conventional common high-frequency limiter. In FIG. 1, an oscillation signal of a magnetron 101 is transmitted from an antenna 103 via a circulator 102. The signal reflected on a target object and received by the antenna 103 passes through a high-frequency limiter 104 via the circulator 102, and is then given to a reception module 105.
The limiter 104 protects the reception module 105 from high-power microwaves directly reflected on the antenna 103 or high power microwaves inputted after directly leaked from the circulator 102, and typically uses a PIN diode. The PIN diode functions as a switch for switching on and off according to the input power, and at the time of a high-power input, the PIN diode is switched to on to short-circuit the circuit to achieve a function of the limiter. Such a characteristic is referred to as a “cutoff characteristic. On the other hand, for a small-power input, such as a reflected wave from a target object, the PIN diode turns off, and a signal component is inputted into the reception module 105 as it is without attenuating. Such a characteristic is referred to as a “transmission characteristic.”
FIG. 2 is a cross-sectional view showing a configuration example of the high-frequency limiter 104 shown in FIG. 1. A tuning block 2 formed with a post 3 projecting from a central part thereof is provided at a predetermined position of a waveguide section 1. A turning choke 5 is provided in a tip-end part of the post 3, and a limiter diode 4 is inserted in an intermediate part of the post 3.    Nonpatent Document 1: Nippon Foundation Library “2003 Marine Vessel Electrical Equipment Technical Lecture for Correspondence Course (Radar and Instrument Maintenance Edition), 4·3, Transmission-and-reception Switching Circuit,” [Online], [Searched on May 7, 2007], Internet <http://nippon.zaidan.info/seikabutsu/2003/00138/contents/0020.htm>
FIG. 16 is views showing a configuration of a conventional waveguide-type high-frequency limiter constituted by using a PIN diode, where FIG. 16(a) shows a cross-sectional view and FIG. 16(b) shows a side view.
In a high-frequency limiter 400 shown in FIG. 16, a diode 401 having a thick I-layer with a sufficient power-proof characteristic is arranged inside a resonance part 403, and a diode 402 having a thin I-layer with a sufficient cutoff characteristic is arranged inside a resonance part 404. Thus, the resonance part 403 and the resonance part 404 are electrically coupled to simultaneously realize tolerance over high power and a short response time (sufficient cutoff characteristic).
Further, an interval between the resonance parts 403 and 404 is set to an odd number multiple of ¼ wavelength of an electromagnetic wave outputted and inputted to constitute a ¼-wave coupled circuit. By constituting as above, because phases of reflected waves reflected on the respective resonance parts are inverted, the reflected waves cancel each other to make matching conditions and thereby input signals are inputted into the circuit without loss.    [Patent Document 1] JP1995-85521(B)    [Patent Document 2] JP1995-22249(B)